Rust, MAKE_JOBS, and "failed to spawn helper thread"

[nia <nia%NetBSD.org@localhost>]

Hi, anyone else seeing this failure when compiling Rust crates on NetBSD
with a high number of parallel jobs? I see this for nearly every crate
in my pbulk builds.

Is there a system limit that needs to be adjusted?

thread 'rustc' panicked at 'failed to spawn helper thread: Os { code: 35, kind:
WouldBlock, message: "Resource temporarily unavailable" }', /tmp/work/lang/rust/
work/rustc-1.54.0-src/compiler/rustc_codegen_ssa/src/back/write.rs:1015:10
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues
/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.54.0 running on x86_64-unknown-netbsd

note: compiler flags: -C opt-level=3 -C lto -C codegen-units=1 --crate-type bin

note: some of the compiler flags provided by cargo are hidden

query stack during panic:  
end of query stack
error: could not compile `bat`   

To learn more, run the command again with --verbose.
*** Error code 101